The long-term goal of this research is to explore the molecular mechanisms that bacteria use for cell-cell communication (i.e., quorum sensing). Until recently, the ability of bacteria to communicate was considered an anomaly that occurred only in a few marine vibrio species. It is now clear that cell-cell communication is the norm in the bacterial world and that understanding this process is fundamental to all of microbiology, including industrial and clinical microbiology, and ultimately to understanding the development of higher organisms. Here we propose an integrative chemical, structural, and biological study of a recently identified quorum-sensing circuit whose functioning depends on the production and detection of a small molecule signal called autoinducer-2 (AI-2). AI-2, unlike other known bacterial auto inducers, is a universal quorum-sensing signal that mediates communication among different bacterial species. We propose to collaborate with the MLPCN to carry out high-throughput screens to identify inhibitors of the AI-2 synthase, LuxS and the AI-2 receptor, LuxPQ. Follow up studies to further characterize the lead compounds identified from the screens will combine synthetic organic chemistry, bacterial genetics, biochemistry, and X-ray crystallography. Antagonists of the AI-2 signaling pathway identified through this work will provide lead compounds for the development of broad-spectrum antibacterial drugs designed to interfere with quorum sensing which could have enormous ramifications for bettering human health. PUBLIC HEALTH RELEVANCE: Until recently, the ability of bacteria to communicate was considered an anomaly that occurred only in a few marine vibrio species. It is now clear that cell-cell communication is the norm in the bacterial world and that understanding this process is fundamental to all of microbiology, including industrial and clinical microbiology. The investigations proposed here will facilitate the development of synthetic strategies for controlling quorum sensing. Specifically, antagonists of the AI-2 signaling pathway identified through this work will provide lead compounds for the development of broad-spectrum antibacterial drugs which could have enormous ramifications for bettering human health.